Virulence of Puccinia striiformis on wheat and barley in central Alberta

Sixty-one field collections of Puccinia striiformis, primarily from central Alberta during 2007-2008, were identified to be P. striiformis f. sp. tritici (Pst) or P. striiformis f. sp. hordei (Psh) based on virulence on differential seedlings. Wheat differentials separated 38 Pst isolates into 13 pathotypes, with most pathotypes consisting of single isolates. Two pathotypes consisted of two isolates, and three pathotypes were represented by three, seven and 16 isolates. Wheat lines with resistance genes Yr1, Yr5, Yr15 and YrSP were resistant to all 13 pathotypes, while wheat lines with genes Yr10, Yr24 and Yr28 were resistant to 82-92% of the isolates. Differentials YrA, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr26, Yr27, Yr31 and YrCV were susceptible to 71-100% of the isolates. Twenty-three Psh isolates were identified to 15 Psh pathotypes, with virulence on two to eight barley differentials, including 'Topper', 'Hiproly', 'Varunda', 'Abed Binder 12', 'Trumpf', 'Mazurka', 'Bigo', 'I 5' and 'Bancroft' and avirulent on 'Heils Franken', 'Emir' and 'Astrix'. Ten pathotypes consisted of a single isolate, four pathotypes had two isolates and one pathotype consisted of five isolates. The possible origin and virulence of P. striiformis pathotypes in central Alberta is discussed in relation to using cultivar resistance for disease control.